Hey,

sometimes not all of my heaters work. Only my drivers side lets out hot air, the others are cold! This happens without any warning, they sometimes work and sometimes just emit cold air instead of hot.

Some one else had that on here. It was a silicon bag that had ruptured in the coolant expansion tank.

 

The Silicon was intermittently blocking parts of the heater matrix. It required a new expansion tank and coolant system strip and flush if I remember correctly.

10 hours ago, logiclee said:

Some one else had that on here. It was a silicon bag that had ruptured in the coolant expansion tank.

 

The Silicon was intermittently blocking parts of the heater matrix. It required a new expansion tank and coolant system strip and flush if I remember correctly.

 

That might have been me:

 

Unfortunately (for my wallet) it also needed a new heater matrix as well as the new expansion tank and flush.

Worth saying that the underlying cause was probably a faulty water pump, which allowed the engine to get hot enough to lose some coolant and presumably caused the silica bag to split. (The water pump problem happened just before I found the heater problem.)

Sadly the water pump issue seems common on older Mk3 diesels:

 

 

Edited 25 January, 20197 yr by DavidY

I had the same issue, turned out the matrix was blocked due to my having used radweld in the radiator for a small leak. Garage was able to flush it clear. I have a spare matrix for anyone looking for one.